What is collagen?

Collagen is big structural proteins that help the body to maintain its strength and flexibility, and is found mostly in the dermis, bones, cartilage and tendons, and makes up approximately 25-35% of the protein in the body. This makes collagen the biggest source of protein in humans (Marcus 1996).

Connective tissue is found everywhere in the body and is important for providing structural support, strengthen, stiffen and simply keep the body together. We find connective tissue in tendons, cartilage and ligaments and as we see from picture 1 of the knees structure, these connective tissues are important for its function. The cells of connective tissue are scattered, and between them are plenty of protein collagen fibres which is highly stretchable.

Knee structure collagen

We distinguish between loose and firm connective tissue, where the loose tissue contains few fibres between the cells, while the firm tissue is almost entirely composed of collagen fibres. The loose tissue can be found underneath the skin and mucous membranes, around the glands, between muscle fibres and nerves as well as in and between organs and other tissues. This has great tensile strength and elasticity in all directions. Firm connective tissue is found in tendons and ligaments that attach muscle to bone and bone to bone. Firm tissue has, in tendons, a very high tensile strength in the direction of the fibres, while ligaments have high tensile strength in all directions. Collagen fibres help form the foundation for skin, hair and nails (Scrieber 2007, Sibilla et al. 2015, Flaschmajer et al. 1990).

Vitamin C is important in the synthesis of collagen, in which it interacts with the amino acids proline and hydroxyproline. Vitamin C provides hydrogen and oxygen so that the amino acids can do their part in the production of collagen. If you lack vitamin C the collagen production will decline. Today there are several approved claims for vitamin C in relation to the formation of collagen for normal function of bones, cartilage, skin and blood vessels and that vitamin C contributes to normal energy-yielding metabolism (EFSA, vitamin C claims).

From our mid-20s, the body’s natural production of collagen and elastin decreases and the collagen fibres become weaker. Skin texture changes and results in weaker (and thinner) skin, drier skin and less elasticity, which we all know as fine lines and wrinkles, as well as affecting the connective tissue in the body. It is assumed that we lose collagen at a rate of 1.5% per year, which means a loss of 30% collagen at 45 years of age. Production cells called fibroblasts are constantly forming procollagen and compensates for the degradation of the collagen fibres to maintain the balance. Procollagen is further transformed and twisted together into strong and flexible collagen fibres. In addition, the collagen fibres have a good ability to bind water, which also helps the skin’s surface to be kept full-bodied, smooth and elastic.

In picture 2 you can see how a reduction in collagen fibres affects skin aging. The first image shows a dense and solid structure between the collagen fibres, elastin and hyaluronic acid. As we get older we see that this solid and dense structure becomes weaker and shows as wrinkles. This change continues over the years and the wrinkles will be more prominent.

  1. How the knee is constructed (Source: Shutterstock.com)

2. How a reduction in collagen affects skin aging (Source: Shutterstock.com)

Before protein can be absorbed and transported around the body, it has to be broken down in the stomach into short peptides and amino acids. It appears that the body can easily absorb short peptides and thus utilize these quickly in the body. Some of these peptides have bioactive properties, which means that they can exert positive effects in the body beyond being a nutrient. The focus on biologically active peptides from different protein sources has increased among researchers. Through cell cultures and animal studies researchers have already identified several sequences that look promising. Different areas that has been studied is especially effects on blood pressure regulation, immune system, cancer, pain response and cholesterol (BT insight, Professional proteins).

The two most common types of collagen is Type 1 and Type 2. Type 1 is found throughout the entire body, except in the cartilage tissue, and accounts for most of the collagen in our body. Type 2 is the most important part in cartilage and synovial fluid.

The collagen obtained from fish is of type 1 collagen which is produced and organized in dermal fibroblasts and connective tissue cells in the skin as well as playing an important role in bone tissue. It is not only in relation to the elasticity and structure of the bone, but also in relation to key processes in bone mineralization and metabolism (Marcus 1996). Marine collagen is absorbed up to 1.5 times more efficiently in the body, and the bioavailability is superior to collagen of both bovine or porcine. This is due to its smaller particle size compared to other types of collagen. The smaller particle size allows an easier and faster uptake and transportation of the collagen peptides to the skin, bones and joints for the synthesis of new collagen.

What is the difference between collagen and collagen peptides?

While collagen is big structural proteins, collagen peptides are a hydrolysed form of collagen; shorter peptide chains. The collagen molecules are big which makes it harder for the body to absorb and utilize. The collagen undergoes an enzymatic hydrolysis process in which the product loses its gelling effect and becomes water-soluble. The molecules becomes smaller and thus easier for the body to absorb. The peptides provides the necessary amino acids for the development of connective tissues. An intake of collagen peptides can stimulate and boost the body’s own ability to produce collagen.

Why are marine collagen peptides unique?

Although collagen has a very high content of protein it has a different amino acid profile than the protein you get from cod fillet. This means that the amino acids from the two sources have different functions in the body. Marine collagen contains, such as cod fillet, all the indispensable amino acids, although in much smaller amounts, but in return has a very high content of the amino acids glycine, proline and hydroxyproline. The function of these amino acids is to stimulate cells in the skin, bones and joints and lead to the production of new collagen. This allows collagen to contribute to strengthening connective tissue and bones, as well as support skin. In addition, marine collagen also contains arginine, and both glycine and arginine are used by the body in the formation of creatine.

Glycine contributes to the synthesis of collagen as well as a variety of other proteins. It can also protect organs and tissues by general inflammatory conditions.

Proline is the precursor of hydroxyproline which is involved in the formation of collagen, tendons and ligaments. Proline is therefore important in the treatment of osteoarthritis. Proline is depending on vitamin C for the formation of collagen. The proline productions in the body increases for instance with injuries and after exercise where it builds up damaged muscle fibres. This means that marine collagen can be helpful in the restitution phase after exercise.

Hydroxyproline is the hydroxylation of proline and is depending on vitamin C. Absorption of hydroxyproline signals the body to make collagen. Lack of vitamin C could give unstable collagen molecules and affect collagen in the body.

The effect of marine collagen peptides on the musculoskeletal system and skin

Added value for the musculoskeletal system

Specific collagen peptides proved to significantly increase the expression of collagen types 1 and 3 in fibroblasts from ligaments and tendons of humans. The study concluded that collagen peptides may therefore be an option to treat and prevent changes in ligaments and tendons (Schunck and Oesser, 2013).

Products containing active collagen peptides have long been marketed in the US and European pharmaceutical and food markets. Many scientific and preclinical studies show various positive effects on tendon flexibility, ligament stability, muscle and bone integrity and bone metabolism. Another study investigated the effect of specific fish-derived collagen peptides on collagen expression, post-translational modification and mineralisation in an osteoblastic cell culture (bone cells). Fish collagen peptides were shown to upregulate the gene expression of collagen-modifying enzymes and this effect led to an increased collagen synthesis and positive effects on collagen quality and matrix mineralisation in the osteoblasts (Yamada, Shizuka et al. 2014).

Another study researched the effects of protein supplements in the form of type 1 collagen peptides in combination with resistance training in older men with sarcopenia. The results showed that, compared to placebo, a collagen supplement in combination with resistance training further improved body composition by increasing the fat-free mass and muscle strength, and reducing fat mass in elderly men with sarcopenia (Zdzieblik et al. 2015).

 Anti-aging effect on human skin

Marine collagen hydrolysates has an anti-aging effect on human skin. A recent clinical trial demonstrated a significant increase in skin elasticity in a group of women aged 35-55 years (Proksch et al. 2014).

Reducing skin wrinkles

The same group of scientists from the University of Kiel, Germany, also demonstrated a significant reduction in skin wrinkles after a daily consumption of a collagen hydrolysate (Proksch et al. 2014).

Increasing the skin moisture level

A comprehensive study on the effect of oral collagen peptide supplementation on skin-aging involving clinical trials with Japanese and Caucasian women showed good effect on skin moisture. The fish collagen peptides were shown to increase the skin moisture level by 12% in a period of 8 weeks. A consistent increase in the skin collagen density over 12 weeks was confirmed by increased dermal echogenicity (Asserin et al. 2015).

Studies made on collagen supplements have seen effects at a daily dose of 10 g, for at least one month. One can follow a daily maintenance dose of 5 g. Since collagen is easily soluble, it can be mixed in liquid such as water, juices, shakes, smoothies, or with yogurt, porridge, muesli, etc.

Seagardens products

Seagarden has developed a production line for marine-based collagen peptides to meet the growing demands of the nutraceutical and cosmetic industries worldwide. Nutraceutical defines a product that comes from food but has additional health benefits in addition to having a basic nutritional value. Seagarden focuses on using Nordic wild-caught raw materials from sustainable fishing stocks and wish to contribute to product development and improved documentation for marine products. Our products contain 100% natural ingredients using raw materials of white fish from the crystal clear waters of the North Atlantic Ocean. The fish is processed through a strict cooking process so that the quality and nutrients in the fish are preserved. The finished product is a micro-milled powder which can easily be mixed in liquid. Seagarden marine collagen has a very high protein content (over 90%) and all products are free from artificial additives and preservatives.

Seagarden’s marine collagen is exclusively produced from cod skin (Gadus morhua), harvested from the crystal-clear waters of the North Atlantic. This provides the purest source of 100% natural collagen of high quality available on the market.

Marine collagen is a nutritional supplement and should not replace a varied and healthy diet. It is not a substitute for other animal protein sources, but can be taken as an additional product.


Asserin, Jérome, et al. “The effect of oral collagen peptide supplementation on skin moisture and the dermal collagen network: evidence from an ex vivo model and randomized, placebo‐controlled clinical trials.” Journal of cosmetic dermatology 14.4 (2015): 291-301.

BT innsikt, Profesjonelle proteiner: http://innsikt.bt.no/profesjonelle-proteiner/ Schrieber, R., Gareis, H. (2007) Gelatine Handbook: Theory and Industrial Practice. Wiley-VCH, Weinheim, 347 pp.

EFSA, vitamin C claims:


Flaschmajer, R., MacDonald, ED., Perlish, JS., Brugeson, RE., Fisher, LW. (1990) Dermal collagen fibrils are hybrids of type I and type III collagen molecules. Journal of Structural Biology 105(1-3), 162–169.

Marcus, R., Feldman, D., Kelsey, J. (eds) (1996) Osteoporosis. Academic, New York

Proksch, E., et al. “Oral intake of specific bioactive collagen peptides reduces skin wrinkles and increases dermal matrix synthesis.” Skin pharmacology and physiology 27.3 (2014): 113-119.

Schunck, M., & Oesser, S. (2013). Specific collagen peptides benefit the biosynthesis of matrix molecules of tendons and ligaments. Journal of the International Society of Sports Nutrition, 10(Suppl 1), P23.

Sibilla, S., Godfrey, M., Brewer, S., Budh-Raja, A., Genovese, L. (2015). An overview of the beneficial effects of hydrolysed collagen as a neutraceutical on skin properties: scientific background and clinical studies. The Open Nutraceutical Journal 8, 29-42.

Yamada, Shizuka, et al. “Effects of fish collagen peptides on collagen post-translational modifications and mineralization in an osteoblastic cell culture system.” Dental materials journal 32.1 (2013): 88-95.

Zdzieblik, Denise, et al. «Collagen peptide supplementation in combination with resistance training improves body composition and increases muscle strength in elderly sarcopenic men: a randomised controlled trial.» British Journal of Nutrition 114.08 (2015): 1237-1245.